Brushes are typically composed of a rigid shaft and bristles that are attached to the shaft. The bristles may be made of either natural animal hair, e.g., goat, pony, badger, etc., or synthetic hair, e.g., nylon fibers. The color of natural animal hair bristles is not uniform and may vary both within a brush and from brush to brush. Synthetic bristles may be colorless, or may be produced being colored throughout, with the color frequently differing from batch to batch.
For various marketing and aesthetic reasons, it is frequently desirable to provide the bristles of a given brush with a uniform color. This is particularly so in the cosmetic industry where aesthetic considerations are very important and it is frequently desirable to utilize brush bristles that match or complement in a visually pleasing fashion the color of a given cosmetic product. It also is desirable for marketing reasons to provide brush bristles with a uniform color from brush to brush. Consequently, it has become common for brush manufacturers, particularly manufacturers of brushes for cosmetic use, to dye brush bristles to the desired uniform color.
One of the problems with dyed brush bristles is that excessive dye is often applied to the bristles, which rubs off the bristles onto the product or the application area (or both) when the brush is used. Another problem is that the dyes used do not always adhere to the bristles well, even when applied to the bristles in moderate amount, and consequently rub off during use. Although some dye transfer is acceptable, it is desirable to minimize such dye transfer to avoid dye being visible on the application area or in apparent discoloration of the product being applied.
Heretofore, brushes have been subjectively evaluated for dye transfer by having an inspector use the brush. Such testing is subject to operator variation, particularly inconsistent pressure on the bristles while testing from brush to brush or even while testing the same brush. Such subjective tests are difficult to apply consistently in order to obtain consistently high quality products.
Similarly, it has been difficult to evaluate the relative ability of different brushes to pick-up product for delivery of the product to the application area. It is also difficult to evaluate the relative ability of different brushes to transfer product to an application surface (e.g., the skin) in use. Subjective evaluations for such pick-up capacity and subsequent transfer capacity are difficult to apply consistently in order to ensure that brushes appropriate for a particular product and application are consistently provided.
It is, therefore, an object of this invention to provide a method of testing dyed brushes in a consistent and repeatable fashion to determine whether or not the brushes exhibit excessive dye transfer characteristics. It is another object of the invention to provide a method that permits comparative testing of different dyed brushes to determine their relative dye transfer characteristics. It is another object to provide an apparatus for conducting such testing.
It is also an object of this invention to provide a method of testing brushes in a consistent and repeatable fashion to determine how much product a particular type of brush will pick-up from a source and ultimately transfer to the application area. It is another object to provide an apparatus for conducting such testing.